John Blair's 71 429 Mustang on the Chassis Dyno at the Visteon Employee Car Show 8/12/05
Ever since I had my 429 SCJ engine dyno'ed on an Engine Dyno in 1999, I've wanted to run my car on a Chassis Dyno (which measures HP/Torque at the rear wheels) to see what kind of loss occurs through the powertrain. I finally got the chance to do that when my company sponsored an employee car show and provided a Chassis Dyno for interested participants. The graphs below show that on the Engine Dynomometer Stand, my engine (stock except for Pertronix ignition and roller rockers) did in fact, precisely meet the factory advertised 370 HP when measured at the flywheel. However, since 1972, HP has been measured at the vehicle's rear wheels, not the flywheel - so what kind of power loss do you get when that power is transmitted through a transmission, a rotating driveshaft and translated through the rear axle? Group member Robert Myhrer and Mustang Monthly editor Jeff Ford ran his 71 429 SCJ 4 speed 4.11 Mach 1 on a Chassis Dyno a couple years back (reference Mustang Monthly 429 Mustang Dyno Article ). Initial runs in the 255 HP range eventually yielded Robert 290 HP after tuning between 8 to 10 dyno runs. My best result on the Chassis Dyno after two pulls with my 429 SCJ C6 4.11 Mach 1 was about 240 HP. This equates to a loss of about 36% going through the powertrain. Robert has proven, through tuning that the loss can be reduced to as low as 23%. This means that I could probably improve this reading quite a bit with additional tuning (carb, timing). One other factor Robert has pointed out, since mine is a C6 automatic, versus his a 4 speed, I could expect additional loss due to converter slippage, additional rotating inertia, etc. which could help account for my lower intial pulls (240) versus his (255). Visteon took video of the dyno run - once I get a copy, I'll post the video on the Megasite - the sound of the car on the dyno was awesome!
John B ~ 8/12/05
Additional Chassis Dyno Results from Jimmy Bennick
Jimmy attended a car show in Myrtle Beach SC where there was a portable Chassis Dyno set up where he got these results. Jimmy's car is a 71 429 CJ 4speed 3.25 Mach 1. The only modifications are larger cam and Blue Thunder intake with correct Ford Holley carb, stock exhaust system with Summit Racing brand mufflers. Below are the results with the engine being run to 6000 RPM (277HP and 353 ft/lbs Torque);